Discrete Multi-tone (DMT) is a common multicarrier modulation scheme that has been implemented in many Digital Subscriber Lines (DSL). As used herein “xDSL” is understood to denote any type of DSL service (e.g., ADSL, DMT-based VDSL, etc.).
In a DMT-based xDSL system, Time Domain Equalization (TEQ) is typically used to reduce the delay spread of the twisted copper line channel such that the equalized channel impulse response can be accommodated by the length of the cyclic prefix. When the delay spread of equalized channel is smaller than the length of the cyclic prefix, not only can the intersymbol interference (ISI) be reduced in the time domain, but also the interchannel interference (ICI) can be reduced in the frequency domain since the orthogonality between sub-bands is preserved.
In previous work, TEQ training is performed either purely in the time-domain or purely in the frequency-domain. This may be disadvantageous because of associated increases in memory usage, computational work and complexity. Other drawbacks of existing systems also exist.